I don't have Capital and Ideology close at hand, so I can't check how he worked it out, but consulting some other sources:
- the top 1% in the US apparently have around $45.7T in wealth [1]
- there are around 22M people in the 20-24 age bracket and 23 in the 25-29 age bracket [2]
So suppose there are 5.5M people turning 21 every year. Giving them each $100k (yes, less than the Piketty proposal for the EU, but in the ballpark, and gives us round numbers) would cost $550B/yr at present. If this were funded as a flat wealth tax only on the top 1%, it would amount to around a 1.2% wealth tax, not accounting for evasion etc. So literally, 99% of the population could pay more in taxes, the 1% would be taking a hit, but honestly so long as long-term average returns are more than 1.2% above inflation, you could still have inter-generational wealth that gets bigger over time.
Of course, many would naturally prefer for a wealth tax to be progressive; the ultra-rich should pay a larger share than the pretty-rich. This would have the impact of shrinking long term dynastic piles of wealth, but not fully eliminating them, and reducing the impact on people at the low end of the 1%.
[1] https://www.federalreserve.gov/releases/z1/dataviz/dfa/distr...
[2] https://www.neilsberg.com/research/datasets/5fd2b2bb-3d85-11...